Is your feature request related to a problem?
Currently, in an explain for a sql which produces ProjectOperator, it only shows the field information of ProjectOperator.

However, if a sql-produced ProjectOperator contains alias, its source-related information is missing in the explain, thus users cannot tell whether the plan is right or not.
e.g.

POST _plugins/_sql/_explain
{
  "query": "SELECT (FlightTimeMin + 1) as FlightTimeMinPlusOne FROM opensearch_dashboards_sample_data_flights LIMIT 5"
}


# explain response
{
  "root": {
    "name": "ProjectOperator",
    "description": {
      "fields": "[FlightTimeMinPlusOne]"
    },
    "children": [
      {
        "name": "OpenSearchIndexScan",
        "description": {
          "request": """OpenSearchQueryRequest(indexName=opensearch_dashboards_sample_data_flights, sourceBuilder={"from":0,"size":5,"timeout":"1m","_source":{"includes":["FlightTimeMin"],"excludes":[]}}, searchDone=false)"""
        },
        "children": []
      }
    ]
  }
}

What solution would you like?
Show the information of name which is (FlightTimeMin + 1) or delegate which is +(FlightTimeMin, 1) in the explain of ProjectOperators.

What alternatives have you considered?
A clear and concise description of any alternative solutions or features you've considered.

Do you have any additional context?
Add any other context or screenshots about the feature request here.